Extreme Ultraviolet Mask Blank Production System With Thin Absorber And Manufacturing System Therefor

ABSTRACT

An extreme ultraviolet (EUV) mask blank production system includes: a substrate handling vacuum chamber for creating a vacuum; a substrate handling platform, in the vacuum, for transporting an ultra-low expansion substrate loaded in the substrate handling vacuum chamber; and multiple sub-chambers, accessed by the substrate handling platform, for forming an EUV mask blank includes: a multi-layer stack, formed above the ultra-low expansion substrate, for reflecting an extreme ultraviolet (EUV) light, and an absorber layer, formed above the multi-layer stack, for absorbing the EUV light at a wavelength of 13.5 nm includes the absorber layer has a thickness of less than 80 nm and less than 2% reflectivity.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. Non-Provisional applicationSer. No. 15/438,248, filed Feb. 21, 2017, which is a continuation ofU.S. Non-Provisional application Ser. No. 14/620,114, filed Feb. 11,2015, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 62/023,496 filed Jul. 11, 2014, to each of which priority isclaimed and each of which are incorporated herein by reference in theirentireties.

The present application contains subject matter related to U.S. patentapplication Ser. No. 14/620,123 filed Feb. 11, 2015. The relatedapplication is assigned to Applied Materials, Inc. and the subjectmatter thereof is incorporated herein by reference thereto.

TECHNICAL FIELD

The present invention relates generally to extreme ultravioletlithography blanks, and manufacturing and lithography systems for suchextreme ultraviolet lithography blanks.

BACKGROUND

Extreme ultraviolet lithography (EUV, also known as soft x-rayprojection lithography) is a contender to replace deep ultravioletlithography for the manufacture of 0.0135 micron, and smaller, minimumfeature size semiconductor devices.

However, extreme ultraviolet light, which is generally in the 5 to 100nanometer wavelength range, is strongly absorbed in virtually allmaterials. For that reason, extreme ultraviolet systems work byreflection rather than by transmission of light. Through the use of aseries of mirrors, or lens elements, and a reflective element, or maskblank, coated with a non-reflective absorber mask pattern, the patternedactinic light is reflected onto a resist-coated semiconductor substrate.

The lens elements and mask blanks of extreme ultraviolet lithographysystems are coated with reflective multilayer coatings of materials suchas molybdenum and silicon. Reflection values of approximately 65% perlens element, or mask blank, have been obtained by using substrates thatare coated with multilayer coatings that strongly reflect light withinan extremely narrow ultraviolet bandpass; e.g., 12.5 to 14.5 nanometerbandpass for 13.5 nanometer ultraviolet light.

In view of the need for the increasingly smaller feature size ofelectronic components, it is increasingly critical that answers be foundto these problems. In view of the ever-increasing commercial competitivepressures, along with growing consumer expectations, it is critical thatanswers be found for these problems. Additionally, the need to reducecosts, improve efficiencies and performance, and meet competitivepressures adds an even greater urgency to the critical necessity forfinding answers to these problems.

Solutions to these problems have been long sought but prior developmentshave not taught or suggested any solutions and, thus, solutions to theseproblems have long eluded those skilled in the art.

SUMMARY

An embodiment of the present invention is an extreme ultraviolet (EUV)mask blank production system provides: a substrate handling vacuumchamber for creating a vacuum; a substrate handling platform, in thevacuum, for transporting an ultra-low expansion substrate loaded in thesubstrate handling vacuum chamber; and multiple sub-chambers, accessedby the substrate handling platform, for forming an EUV mask blankincluding: a multi-layer stack, formed above the ultra-low expansionsubstrate, for reflecting an extreme ultraviolet (EUV) light, and anabsorber layer, formed above the multi-layer stack, for absorbing theEUV light at a wavelength of 13.5 nm includes the absorber layer has athickness of less than 80 nm and less than 2% reflectivity.

An embodiment of the present invention is an extreme ultraviolet (EUV)mask blank system provides: an ultra-low expansion substrate; amulti-layer stack over the ultra-low expansion substrate; and anabsorber layer, over the multi-layer stack, with a thickness of lessthan 80 nm and less than 2% reflectivity of an extreme ultraviolet (EUV)light at a wavelength of 13.5 nm.

Certain embodiments of the invention have other steps or elements inaddition to or in place of those mentioned above. The steps or elementwill become apparent to those skilled in the art from a reading of thefollowing detailed description when taken with reference to theaccompanying drawings.

The light source for the next generation lithography is moving on from193 nm wavelength to an extreme ultraviolet source of 13.5 nm. As aresult, the mask blank will move from transmission to the reflectiongeometry. The structure of the mask blank can be a Molybdenum(Mo)/Silicon (Si) multi-layer structure with a period spacing designedfor maximum reflection at 13.5 nm wavelength. An EUV mask blank is acomplex structure, which controls the behavior of light in each layer.Some regions of the mask will reflect light and others will absorb. Theregion where light reflects is due to the constructive interference fromeach interface in the periodic structure of the multilayer, with minimumabsorption. And the region where light is absorbed is due to acombination of thin film absorption and destructive interference fromthe absorber and the multi-layer structure underneath. Embodimentsdisclose single layered films which acts as an absorber for a radiationcentered at 13.5 nm with a bandwidth of 0.5 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an extreme ultraviolet (EUV) mask production system.

FIG. 2 is a cross-sectional view of an EUV mask blank in accordance withan embodiment.

FIG. 3 is an orthogonal view of an EUV mask.

FIG. 4 is a flow chart of a method for making the EUV mask blank withultra-low defects.

FIG. 5 is a flow chart of an alternative method for making the EUV maskblank with ultra-low defects.

FIG. 6 is a functional diagram of an optical train for an EUVlithography system.

FIG. 7 shows a schematic view of an EUV mask blank including an absorberlayer in an embodiment.

DETAILED DESCRIPTION

The following embodiments are described in sufficient detail to enablethose skilled in the art to make and use the invention. It is to beunderstood that other embodiments would be evident based on the presentdisclosure, and that system, process, or mechanical changes may be madewithout departing from the scope of the present invention.

In the following description, numerous specific details are given toprovide a thorough understanding of the invention. However, it will beapparent that the invention may be practiced without these specificdetails. In order to avoid obscuring the present invention, somewell-known circuits, system configurations, and process steps are notdisclosed in detail.

The drawings showing embodiments of the system are semi-diagrammatic andnot to scale and, particularly, some of the dimensions are for theclarity of presentation and are shown exaggerated in the drawing FIGs.Similarly, although the views in the drawings for ease of descriptiongenerally show similar orientations, this depiction in the FIGs. isarbitrary for the most part. Generally, the invention can be operated inany orientation.

Where multiple embodiments are disclosed and described having somefeatures in common, for clarity and ease of illustration, description,and comprehension thereof, similar and like features will be describedwith similar reference numerals.

For expository purposes, the term “horizontal” as used herein is definedas a plane parallel to the plane or surface of a mask blank, regardlessof its orientation. The term “vertical” refers to a directionperpendicular to the horizontal as just defined. Terms, such as “above”,“below”, “bottom”, “top”, “side” (as in “sidewall”), “higher”, “lower”,“upper”, “over”, and “under”, are defined with respect to the horizontalplane, as shown in the figures. The term “on” indicates that there isdirect contact between elements.

The term “processing” as used herein includes deposition of material orphotoresist, patterning, exposure, development, etching, cleaning,and/or removal of the material or photoresist as required in forming adescribed structure.

Referring now to FIG. 1, therein is shown an integrated extremeultraviolet (EUV) mask blank production system 100. The integrated EUVmask blank production system 100 includes a mask blank loading andcarrier handling system 102 having load ports 104 into which transportboxes containing substrates 105, such as substrates of glass, silicon,or other ultra-low thermal expansion material, are loaded. An airlock106 provides access to a substrate handling vacuum chamber 108. In anembodiment, the substrate handling vacuum chamber 108 can contain twovacuum chambers, a first vacuum chamber 110 and a second vacuum chamber112. The first vacuum chamber 110 can contain a first substrate handlingplatform 114 and the second vacuum chamber 112 can contain a secondsubstrate handling platform 116.

The substrate handling vacuum chamber 108 can have a plurality of portsaround its periphery for attachment of various subsystems. The firstvacuum chamber 110 can, for example, have a degas subsystem 118, a firstphysical vapor deposition sub-chamber 120 such as an absorber layerdeposition chamber, a second physical vapor deposition sub-chamber 122such as a backside chucking layer deposition chamber, and a precleansubsystem 124.

The second vacuum chamber 112 can have a first multi-cathode sub-chamber126 such as a multilayer deposition chamber, a flowable chemical vapordeposition (FCVD) sub-chamber 128 such as a planarization layerdeposition chamber, a cure sub-chamber 130, and a second multi-cathodesub-chamber 132 connected to it.

The first substrate handling platform 114 is capable of moving anultra-low expansion substrate, such as a first in-process substrate 134,among the airlock 106 and the various subsystems around the periphery ofthe first vacuum chamber 110 and through slit valves, not shown, in acontinuous vacuum. The second substrate handling platform 116 can movean ultra-low expansion substrate, such as a second in-process substrate136, around the second vacuum chamber 112 while maintaining the secondin-process substrate 136 in a continuous vacuum.

It has been discovered that the integrated EUV mask blank productionsystem 100 can provide an environment for manufacturing EUV mask blanks,while minimizing the manual transport of the first in-process substrate134 and the second in-process substrate 136.

Referring now to FIG. 2, therein is shown a cross-sectional view of anEUV mask blank 200 in accordance with an embodiment. The EUV mask blank200 can have an ultra-low thermal expansion substrate 202 of glass,silicon, or other ultra-low thermal expansion material. The ultra-lowthermal expansion materials include fused silica, fused quartz, calciumfluoride, silicon carbide, silicon oxide-titanium oxide, or othermaterial having a thermal coefficient of expansion within the range ofthese materials.

It has been discovered that a planarization layer 204 can be used forfilling surface imperfections 203, such as pits and/or defects in theultra-low expansion substrate 202, covering particles on top of theultra-low expansion substrate 202, or smoothing an already planarizedsurface of the ultra-low expansion substrate 202 to form a planarsurface 205.

A multi-layer stack 206 can be formed on the planarization layer 204 toform a Bragg reflector. Due to the absorptive nature of the illuminatingwavelengths used in EUV, reflective optics are used. The multi-layerstack 206 may be made of alternating layers of high-Z and low-Zmaterials, such as molybdenum and silicon in order to form a reflector.

A capping layer 208 is formed on the multi-layer stack 206 opposite theultra-low expansion substrate 202 for forming a capped Bragg reflector.The capping layer 208 can be a material such as Ruthenium (Ru) or anon-oxidized compound thereof to help protect the multi-layer stack 206from oxidation and any chemical etchants to which the EUV mask blank 200may be exposed during subsequent mask processing. Other material such astitanium nitride, boron carbide, silicon nitride, ruthenium oxide, andsilicon carbide may also be used in the capping layer 208.

An absorber layer 210 can be formed on the capping layer 208. Theabsorber layer 210 can be of a material having a high absorptioncoefficient for a particular frequency of EUV light (about 13.5 nm) andmay be a material such chromium, tantalum or nitrides thereof. As anexample, a thickness 211 of the absorber layer 210, formed of chromium,tantalum or nitrides thereof, can be greater than 80 nm. The absorberlayer 210, formed of chromium, tantalum or nitrides thereof, can have areflectivity of greater than 2%.

The absorber layer 210 must be kept as thin as possible in order toreduce the surface parallax that causes shadowing in a mask formed onthe EUV mask blank. One of the limitation with the absorber layer 210,formed of chromium, tantalum or nitrides thereof having the thickness211 greater than 80 nm, is that the angle of incidence of the EUV lightcan cause shadowing which limits that pattern size that can achieved inan integrated circuit produced by a mask using the EUV mask blank, whichlimits the size of integrated circuit devices that can be fabricated.

The absorber layer 210 can be formed of a single layer of less than 80nm by using one of the following metals Nickel (Ni), Platinum (Pt),Silver (Ag), Zinc (Zn), Tin (Sn), Gold (Au), Hafnium (Hf), Lead (Pb),Indium (In), Cadmium (Cd), or semimetals Bismuth (Bi), Antimony (Sb),and Tellurium (Te), The material of the absorber layer 210 are chosenfor their absorption characteristics at 13.5 nm and for their ability tobe etched. The absorber layer 210 can be deposited by PVD, CVD, ALD, RF,and DC magnetron sputtering techniques. The absorber layer 210 canoperate by a combination of thin film absorption and destructiveinterference of the EUV light.

The percent of reflectivity, provided by the EUV mask blank 200, can becontrolled by managing the thickness 211 of the absorber layer 210. Byway of an example, percent of reflectivity of the EUV light at thewavelength of 13.5 nm can be controlled to 5%, 3%, 1%, or 0.5% based onthe thickness 211 of the absorber layer 210.

An anti-reflective coating (ARC) 212 can be deposited on the absorberlayer 210. The ARC 212 can be of a material such as tantalum oxynitrideor tantalum boron oxide.

A backside chucking layer 214 can be formed on the back-side surface ofthe ultra-low expansion substrate 202, opposite the planarization layer204, for mounting the substrate on or with an electrostatic chuck (notshown).

Referring now to FIG. 3, therein is shown an orthogonal view of an EUVmask 300. The EUV mask 300 can be a rectangular shape and can have apattern 302 on the top surface thereof. The pattern 302 can be etchedinto the ARC 212 and the absorber layer 210 to expose the capping layer208, for representing the geometry associated with a step in themanufacturing of an integrated circuit, not shown. The backside chuckinglayer 214 can be applied on the backside of the EUV mask 300 oppositethe pattern 302.

Referring now to FIG. 4, therein is shown a flow chart of a method 400for making the EUV mask blank 200 with ultra-low defects. The ultra-lowdefects are substantially zero defects. The method 400 includes theultra-low expansion substrate 202 of FIG. 2 being supplied at an inputsubstrate step 402. The ultra-low expansion substrate 202 can bebackside cleaned in a substrate cleaning step 404, degassed andpre-cleaned in a backside prep step 406.

The backside chucking layer 214 of FIG. 2 is applied to the back-side ofthe ultra-low expansion substrate 202 in a deposit backside chuckinglayer step 408 and a front-side clean can be performed in a front-sidecleaning step 410. The substrates 105, after the front-side cleaningstep 410, can be input to the first vacuum chamber 110 for furtherprocessing. The steps of forming a capped Bragg reflector 412 are betterperformed in the integrated EUV mask blank production system 100 of FIG.1 while under continuous vacuum to avoid contamination from ambientconditions.

A degas and preclean step 414 and planarization step 416 can beperformed in the first vacuum chamber 110. The planarization layer 204of FIG. 2 can be cured in a planarization layer cure step 418 and thedeposition of the multi-layer stack 206 of FIG. 2 can be performed in adepositing the multi-layer stack step 420. Both the planarization layercure step 418 and the multi-layer stack step 420 can be performed in thesecond vacuum chamber 112. The capping layer 208 of FIG. 2 can bedeposited in a depositing a capping layer step 422 within the secondvacuum chamber 112 for forming the second in-process substrate 136, suchas the capped Bragg reflector.

After exiting the integrated EUV mask blank production system 100, thesecond in-process substrate 136 is subjected to a deep ultraviolet(DUV)/Actinic inspection, which can be performed in an inspection step424, the second in-process substrate 136 can be optionally cleaned in asecond front-side cleaning step 426, and the absorber layer 210 of FIG.2 and anti-reflective coating 212 of FIG. 2 can be deposited in an EUVmask blank completion step 428 for forming the EUV mask blank 200 ofFIG. 2.

It has been discovered that the integrated EUV mask blank productionsystem 100 can produce the EUV mask blank 200 consistently withsubstantially zero defects. The Application of the planarization layer204 in the first vacuum chamber 110 and the curing of the planarizationlayer 204 in the second vacuum chamber 112 can improve the efficiency ofthe integrated EUV mask blank production system 100 because the chambersdo not require thermal ramp time between the deposition of theplanarization layer 204 and its curing.

Referring now to FIG. 5, therein is shown a flow chart of an alternativemethod 500 for making the EUV mask blank 200 with ultra-low defects. Theultra-low defects are substantially zero defects. The alternative method500 begins with the ultra-low expansion substrate 202 of FIG. 2 beingsupplied in an input substrate step 502. The ultra-low expansionsubstrate 202 can be cleaned in a back-side cleaning step 504 andfront-side can be cleaned in a front-side cleaning step 506.

The steps of forming a capped Bragg reflector 508 are better performedin the integrated EUV mask blank production system 100 of FIG. 1 whileunder continuous vacuum to avoid contamination from ambient conditions.

The substrates 105 can be degassed and pre-cleaned in a vacuum cleaningstep 510 performed in the degas subsystem 118. The backside chuckinglayer 214 can be deposited in a deposit backside chucking layer step 512and planarization occurs in a planarization step 514. The planarizationlayer 204 of FIG. 2 can be cured in a planarization curing step 516,which can be performed in the cure subsystem 130. The deposition of themulti-layer stack 206 of FIG. 2 can be performed in a depositing themulti-layer stack step 518 and the capping layer 208 of FIG. 2 can bedeposited in a depositing a cap deposition step 520 for forming thesecond in-process substrate 136.

While the DUV/Actinic inspection may be performed inside the integratedEUV mask blank production system 100, it may occur also outside in aninspection step 522. The second in-process substrate 136 can beoptionally cleaned in a second cleaning step 524, and the absorber layer210 of FIG. 2 and anti-reflective coating 212 of FIG. 2 can be depositedin an EUV mask blank completion step 526.

Referring now to FIG. 6, therein is shown a functional diagram of anoptical train 600 for an EUV lithography system. The optical train 600has an extreme ultraviolet light source 602, such as a plasma source,for creating the EUV light and collecting it in a collector 604. Thecollector 604 can have a parabolic shape for focusing the EUV light on afield facet mirror 608. The collector 604 provides the light to thefield facet mirror 608 which is part of an illuminator system 606.

The surface of the field facet mirror 608 can have a concave contour inorder to further focus the EUV light on a pupil facet mirror 610. Theilluminator system 606 also includes a series of the pupil facet mirror610 for transferring and focusing the EUV light on a reticle 612 (whichis the fully processed version of the substrates 105 of FIG. 1).

The reticle 612 can have a pattern that represents a processing layer ofan integrated circuit. The reticle 612 reflects the EUV, light includingthe pattern, through projection optics 614 and onto a semiconductorsubstrate 616. The projection optics 614 can reduce the area of thepattern provided by the reticle 612 and repeatedly expose the patternacross the surface of the semiconductor substrate 616.

Referring now to FIG. 7, therein is shown a schematic view of the EUVmask blank 200 including the absorber layer 210 in an embodiment.Several candidates for the absorber layer are documented in thisinvention. The absorber layer 210 can be patterned to control absorptionand dispersion of 13.5 nm light in single layers of metals andsemimetals. The absorber layer 210 can be deposited on a capped Mo/Simulti-layer stack 702 opposite the ultra-low expansion substrate 202. Anembodiment provides that the capping layer 208 can be a thin Rutheniumlayer of 2.5 to 3 nm in thickness.

The behavior of the absorber layer 210 can be predicted on the cappedMo/Si multi-layer stack 702. The multi-layer stack 206 can be replicated60 or more times, with a 1.7 nm layer of a molybdenum silicide layer 704at the base of each interface. As an example, an embodiment of each ofthe multi-layer stack 206 includes a 2 nm layer of a Molybdenum (Mo)layer 706 formed on the molybdenum silicide layer 704. A 1 nm layer of aMolybdenum Silicide (MoSi) layer 708 formed on the Molybdenum (Mo) layer706. A Silicon (Si) layer 710 of a 2.26 nm thick layer can be formed atthe top of each of the multi-layer stack 206.

An additional multi-layer stack 712 can be formed directly on theplanarization layer 204. It is understood that the additionalmulti-layer stack 712 can include up to 60 of the multi-layer stack 206formed in a vertical stack above the ultra-low expansion substrate 202.

As an example, the thickness 211 of the absorber layer 210 can be in therange of between 10 nm and 83 nm, in order to provide between 95% and99.5% absorption of the EUV light at 13.5 nm. The percent ofreflectivity, provided by the EUV mask blank 200, can be controlled bymanaging the thickness 211 of the absorber layer 210. By way of anexample, percent of reflectivity of the EUV light at the wavelength of13.5 nm can be controlled to 5%, 3%, 1%, or 0.5% based on the thickness211 of the absorber layer 210, as shown in Table 1.

All the reflectivity results can be verified with the Fresnel equationsat each interface using the Parratt's exact recursive method. Thefollowing metals Nickel (Ni), Platinum (Pt), Silver (Ag), Zinc (Zn), Tin(Sn), Gold (Au), Hafnium (Hf), Lead (Pb), Indium (In), Cadmium (Cd)along with semimetals Bismuth (Bi), Antimony (Sb), and Tellurium (Te)are chosen, for use in the absorber layer 210, for their absorptioncharacteristics at 13.5 nm and for their etchability. The absorber layer210 can have a thickness 211 in the range of 31 nm to 83 nm to establisha maximum percent of absorption, greater than or equal to 99%, of theEUV light at the wavelength of 13.5 nm. The absorber layer 210 can bedeposited by PVD, CVD, ALD, RF and DC magnetron sputtering techniques.These metals can form a very thin layer of native oxide, which has verylittle affect on the absorption and phase shift behavior at a wavelengthof 13.5 nm. Table 1 gives the required thickness 211 for each metal toachieve an overall reflectivity of 5, 3, 1, and 0.5%.

TABLE 1 Thickness (nm) required to achieve reflectivity of Absorber 5%3% 1% 0.5% Ni 17.95 18.9 32.7 40.5 Pt 20.2 27.5 43.6 — Ag 13 19.9 35.5 —Zn 24.2 30.7 39.1 52.5 Sn 18.1 19.1 33 40.9 Au 20.7 28 50.6 — Hf 39.146.5 67.7 82.2 Pb 26 33 48 62.7 In 18.5 19.4 33.6 48.2 Cd 19.9 26.8 41.556.4 Bi 24.8 26.2 40.4 54.6 Sb 18.3 24.8 33 40.7 Te 17.4 18.4 31.5 38.8

The atomic scattering factors of these chosen elements have higher realand imaginary parts than most elements in the periodic table. The higherimaginary part accounts for the absorption and the real part correspondsto the ability to modulate the phase of the incident EUV light. Thephase modulation also depends on the thickness 211 of the absorber layer210, since it's related to the path difference induced phase shift.

The resulting method, process, apparatus, device, product, and/or systemis straightforward, cost-effective, uncomplicated, highly versatile,accurate, sensitive, and effective, and can be implemented by adaptingknown components for ready, efficient, and economical manufacturing,application, and utilization.

Another important aspect of the present invention is that it valuablysupports and services the historical trend of reducing costs,simplifying systems, and increasing performance.

These and other valuable aspects of the present invention consequentlyfurther the state of the technology to at least the next level.

While the invention has been described in conjunction with a specificbest mode, it is to be understood that many alternatives, modifications,and variations will be apparent to those skilled in the art in light ofthe aforegoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications, and variations that fall within thescope of the included claims. All matters hithertofore set forth hereinor shown in the accompanying drawings are to be interpreted in anillustrative and non-limiting sense.

What is claimed is:
 1. An extreme ultraviolet (EUV) mask blankcomprising: an ultra-low expansion substrate; a multi-layer stack overthe ultra-low expansion substrate; and an absorber layer, over themulti-layer stack, with a thickness of less than 80 nm and less than 2%reflectivity of an extreme ultraviolet (EUV) light at a wavelength of13.5 nm, wherein the absorber layer includes a single layer of Nickel(Ni), Platinum (Pt), Silver (Ag), Zinc (Zn), Tin (Sn), Gold (Au), Lead(Pb), Indium (In), Hafnium (Hf), Cadmium (Cd), Bismuth (Bi), Antimony(Sb), or Tellurium (Te); and an anti-reflective coating on the absorberlayer, the anti-reflective coating selected from tantalum oxynitride andtantalum boron oxide.
 2. The extreme ultraviolet (EUV) mask blank ofclaim 1, further comprising a capping layer formed on the multi-layerstack, the capping layer comprising at least one material selected fromthe group consisting of titanium nitride, boron carbide, and siliconcarbide.
 3. The extreme ultraviolet (EUV) mask blank of claim 1, furthercomprising an additional multi-layer stack formed between the ultra-lowexpansion substrate and the absorber layer.
 4. The extreme ultraviolet(EUV) mask blank of claim 1, further comprising an additionalmulti-layer stack formed directly on a planarization layer and themulti-layer stack formed on the additional multi-layer stack.
 5. Theextreme ultraviolet (EUV) mask blank of claim 1, wherein the absorberlayer includes a single layer of Tin (Sn).
 6. The extreme ultraviolet(EUV) mask blank of claim 1, wherein the absorber layer includes asingle layer of Lead (Pb).
 7. The extreme ultraviolet (EUV) mask blankof claim 1, wherein the absorber layer includes a single layer ofBismuth (Bi), Antimony (Sb), or Tellurium (Te).
 8. The extremeultraviolet (EUV) mask blank of claim 1, wherein the absorber layer isin a range of 10 nm to 83 nm thick.
 9. An extreme ultraviolet (EUV) maskblank system comprising: an ultra-low expansion substrate; a multi-layerstack over the ultra-low expansion substrate; and an absorber layer,over the multi-layer stack, with a thickness of less than 80 nm and lessthan 2% reflectivity of an extreme ultraviolet (EUV) light at awavelength of 13.5 nm, wherein the absorber layer includes a singlelayer of Nickel (Ni), Platinum (Pt), Silver (Ag), Zinc (Zn), Tin (Sn),Gold (Au), Lead (Pb), Indium (In), Hafnium (Hf), Cadmium (Cd), Bismuth(Bi), Antimony (Sb), or Tellurium (Te); and a capping layer formed onthe multi-layer stack, the capping layer comprising at least onematerial selected from the group consisting of titanium nitride, boroncarbide, and silicon carbide.
 10. The extreme ultraviolet (EUV) maskblank of claim 9, further comprising an additional multi-layer stackformed between the ultra-low expansion substrate and the absorber layer.11. The extreme ultraviolet (EUV) mask blank of claim 9, furthercomprising an additional multi-layer stack formed directly on aplanarization layer and the multi-layer stack formed on the additionalmulti-layer stack.
 12. The extreme ultraviolet (EUV) mask blank of claim9, wherein the absorber layer includes a single layer of Tin (Sn). 13.The extreme ultraviolet (EUV) mask blank of claim 9, wherein theabsorber layer includes a single layer of Lead (Pb).
 14. The extremeultraviolet (EUV) mask blank of claim 9, wherein the absorber layerincludes a single layer of Bismuth (Bi), Antimony (Sb), or Tellurium(Te).
 15. The extreme ultraviolet (EUV) mask blank of claim 9, whereinthe absorber layer is in a range of 10 nm to 83 nm thick.